Inherently conductive polymers (ICPs) are an important class of materials recognized by the Nobel Prize in Chemistry for the year 2000. Since the seminal publication (Shirakawa, Hideki; Louis, Edwin J.; MacDiarmid, Alan G.; Chiang, Chwan K.; Heeger, Alan J. J. Chem. Soc. Chem. Commun., 1977, 578) in this field, many conducting polymers have been developed but few are available commercially. This in part is due to cost as well as insufficient dispersibility. See (Gregory, Richard V. Chapter 18: Solution Processing of Conductive Polymers: Fibers and Gels from Emeraldine BasePolyaniline in Handbook of Conducting Polymers, Eds. Skotheim, Terje A.; Elsenbaumer, Ronald L.; Reynolds, John R.; MarcelDekker Inc., 1998; p. 437) for many applications. Also see, Lignosulfonic Acid-Doped Polyaniline (Viswanathan, T. “Conducting Compositions of Matter”, U.S. Pat. No. 6,299,800 (2001)).
LIGNO-PANI™, however, is an inexpensive dispersible ICP available commercially on an industrial scale (http://www.polyone.com). The decreased cost as well as increased dispersibility of LIGNO-PANI™ is due to the incorporation of lignosulfonic acid as a polymeric dopant/template (Sudhakar, M.; Toland, A. D.; Viswanathan, T. Chapter 6. Conducting Waterborne Lignosulfonic Acid-Doped Polyaniline in Semiconducting Polymers. Eds. Hsieh, Bing R.; Wei, Yen; American Chemical Society, 1999; p. 76).
Lignin, a renewable resource, is a waste product from the paper industry. The sulfonated form of lignin is therefore inexpensive and highly water soluble. An important property of LIGNO-PANI™ is that the polymeric dopant is permanently incorporated into the ICP resulting in electroactivity at higher pH values than other polyanilines (Berry, B. C.; Shaikh, A. U.; Viswathan, T. ACS Polymer Preprints. 2000, 41, 327). Composites of ICPs and carbon black have also been explored (Avlyanov, J., Dahman, S. Chapter 17. Thermally Stable Intrinsically Conductive Polymer-Carbon Black Composites as New Additives for Plastics in Semiconducting Polymers. Eds. Hsieh, Bing R.; Wei, Yen; American Chemical Society, 1999; p. 76). These composites demonstrate high conductivities as well as improved properties over carbon black alone for some applications.
Carbon black and graphite possess good conductive properties but are highly insoluble in aqueous and organic systems. Composites of carbon black and inherently conductive polymers (ICPs) such as polyaniline (PANi) have been studied but the conductivity of these composites is limited to the conductivity of the PANi. For example, U.S. Pat. No. 5,498,372 to Hedges discloses a carbon allotrope composite formed with an ICP having a highest conductivity of the conducting polymer component. (U.S. Pat. No. 5,498,372, 1996, to Hedges). These prior art composites presented an advance over existing technology because the carbon black/ICP composites allowed for easy control of resistivity in the range needed for electrostatic dissipation (ESD). Furthermore, the prior art composites exhibited improved thermal stability over existing technology at the time (see, Avlyanov, J., Dahman, S. Chapter 17. Thermally Stable Intrinsically Conductive Polymer-Carbon Black Composites as New Additives for Plastics in Semiconducting Polymers. Eds. Hsieh, Bing R.; Wei, Yen; American Chemical Society, 1999; p. 76). Highly conductive carbon/ICP composites are desirable for the increased resistivity control and better thermal stability, however, a considerable need exists in the art for a dispersible composite that possesses high conductivity.